N-methylol compounds have been used extensively in the treatment of cotton containing fabrics for imparting durable press properties. The most extensively used class of compounds are N-methylol derivatives of amides such as dihydroxyethyleneurea, ethyleneurea, carbamates, triazones, uron and melamine which are applied in rapid pad-dry-cure processes. Fabrics modified by reaction with these amide derivatives have excellent durable press properties but retain only a small fraction of their original strength and abrasion resistance. Significant progress was made toward overcoming this drawback in a process termed wet-fixation which was first disclosed by Getchell in U.S. Pat. No. 3,138,802. Basically, the process involves padding the fabric with a combination of two reagents, a polymer forming N-methylol melamine and a crosslinking agent such as dimethyloldihydroxyethyleneurea, in the presence of a mineral acid catalyst. The wet fabric is held in a flat and wet state for as long as 24 hours at room temperature, for 15 minutes at 80.degree. C, or for shorter periods at higher temperatures, after which the catalyst is neutralized and the unreacted reagents removed by washing. Recatalysis, drying, and curing complete the treatment. The improved strength properties observed in durable press fabrics prepared by the wet fixation process are generally attributed to a deep even penetration of the monomers into the cellulose fibers prior to fixation as part of a three dimensional network copolymer.
Recently a more rapid technique for fixing the reagent has been disclosed by Hollies in U.S. Pat. No. 3,709,657. In this process the wet impregnated fabrics are held under non-evaporative, hot conditions, (100.degree.-140.degree. C) for short times (10-90 sec.). This improved process nevertheless involves an additional fixation and washing step which is not desirable in industrial practice.
The prior art in the field of durable press thus suffers two distinct disadvantages. The pad-dry-cure process employing conventional N-methylolamides is satisfactory for mill operation and yields fabrics with high levels of resilience but the treated fabrics have significantly reduced strength and abrasion resistance. The wet fixation technique gives products with good resilience and strength properties but the treatment involves two stages which is undesirable from a processing point of view.